The present invention relates generally to a warewasher for washing dishes, utensils, glasses and the like in commercial establishments, such as restaurants, particularly "fast food" restaurants and cafeterias, and more particularly, to an improved latch mechanism for a front-loading commercial warewasher.
The terms "warewasher" and "dishwasher" may be used interchangeably herein. Further, the term "commercial" dishwasher (to which this invention is directed), is intended to distinguish from a "domestic" dishwasher, the type commonly found in home use. Domestic and commercial dishwashers differ substantially in design and manner of use, even though a few commercial machine designs, which are an outgrowth of domestic designs, may have appearances similar to their domestic forerunners. These latter designs still differ in function and operation both in the length of time it takes to wash and rinse a rack of ware, and also in the number of washes and rinses per rack. These differences are dictated by the differing requirements for commercial machines as opposed to domestic machines. For example, it is rare in a domestic environment to wash consecutive racks or loads of ware; whereas, it is routine in the commercial environment, such as at a restaurant, where an operator may wash one rack of ware after another during and after a lunch period.
In addition to washing and rinsing, domestic machines ordinarily have the further capability of drying washed dishes within the wash chamber, whereas, commercial units utilize air drying outside the chamber in order to minimize the time it takes to complete each rack of ware. The drying operation within the wash chamber of a domestic machine requires a substantial portion of the 60-90 minutes required to complete an operating cycle for a single rack of ware in the domestic machine. By comparison, a commercial dishwasher will wash and rinse a rack of ware in 2-3 minutes or less, with the cleansed rack of ware being immediately removed and replaced by the next rack of soiled ware to be washed. Cleansed ware is then air dried in the racks outside the dishwasher. It is thus important in a commercial environment to wash racks of ware successively in rapid order, and accordingly, a commercial warewasher is used for washing and rinsing, but not for drying because of the length of time drying takes.
The kind of commercial dishwasher to which this invention is applicable is commonly referred to as a front-loading "stationary rack machine." Such a machine includes a wash chamber having a front opening which is closed by a pivotally-mounted door. A rack of soiled ware is deposited into the wash chamber, washed, rinsed and then removed and replaced by a second rack of soiled ware while the cleansed rack is air dried outside the chamber. For simplicity of operation and to facilitate rapid washing for consecutive racks or loads of ware in such a front-loading commercial warewasher, it is desirable to have complete closure of the machine door operate a switch signaling that a soiled rack of ware has been inserted into the machine and that a machine cycle is to be initiated. Accordingly, for a series of racks to be consecutively washed after a first rack, all that is required to operate the warewasher is that each washed rack be removed from the machine, a soiled rack of ware be inserted into the machine, and the door be completely closed. Such operation is described in U.S. patent application Ser. No. 833,946, filed Feb. 26, 1986, which is entitled "Low Energy, Low Water Consumption Warewasher and Method," is assigned to the same assignee as the present application and is incorporated herein by reference.
While door switch activation of the warewasher machine is advantageous to expedite operations during busy times, such operation can lead to wasted water and energy if the door is inadvertently fully closed while the wash chamber is empty. Under such circumstances, the warewasher proceeds through its normal operating cycle with the standard usage of electricity for operating the warewasher and hot water for rinsing the ware. In addition, in the warewasher of the referenced patent application, a booster heater may be provided to raise the temperature of incoming water to a sufficiently high sanitizing temperature, such as 180.degree. F., and accordingly, booster heater energy may also be consumed. In accordance with the timing control mechanism of the referenced patent application, the booster heater is set to maintain the temperature of the water therein for a period of one hour, with the timer for the booster heater being reset each time the warewasher door is completely closed. Hence, if a booster heater is provided, not only would the electrical energy and hot water required for a single wash/rinse operating cycle be wasted, but the time during which the booster heater is activated would be extended by the inadvertent full or complete closure of the warewasher door.
To overcome these problems and ensure that the warewasher door is only fully closed after a rack of soiled ware has been placed into the wash chamber, a number of interlocking latch arrangements can be envisioned. For example, a spring-loaded bolt which would have to be retracted to allow complete closure of the door could be used to prevent one from moving the door to a vertical position out of the way, yet prevent the door from being fully closed unless full closure was intended. However, this as well as other apparent arrangements tend to be complicated and could interfere with the smooth and rapid operation of the warewasher during busy periods.
It is, therefore, apparent that a rugged, simple and inexpensive latch mechanism for a front-loading commercial warewasher is needed to positively prevent the inadvertent closure of the warewasher door while permitting its rapid and complete intentional closure.